Nice. This image gave me an idea. It might be possible to use a modified water shader on a regular entity and somehow mask out certain areas based on a texture map and thus create the effect that there are puddles on a surface. Just a thought. I'm not sure exactly how it could be implemented, but I might give it a try someday.
System Specs: OS - Windows 7 Home Premium 64-bit SP1, CPU - AMD Phenom II X4 945, 3.0Ghz, RAM - 8Gb DDR3, GFX Card - 2048MB NVIDIA GeForce GT 640, FPSC-R Version - Beta 1.0071